<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>字符串大小写转换</title>
    <style>
    input{
        margin-bottom: 30px;
    }
    </style>
</head>
<body>
    <h2>大小写转换</h2>
    原数据：<input id="old" type="text">
</br>
    操  作：
        <input type="button" value="转大写" onclick="deal('upper')">
        <input type="button" value="转小写" onclick="deal('lower')">
</br>
    新数据：<input id="new" type="text">
    <script>
        function deal(opt){
            var str=document.getElementById('old').value;
            switch(opt){
                case 'upper':
                   str=str.toUpperCase();
                   break;
                case 'lower':
                   str=str.toLowerCase();
                   break;
            }
            document.getElementById('new').value=str;
        }
    </script>
    <p><a href="第四章作业.html">返回</a></p>
</body>
</html>